As a technology of inspecting an integrated circuit, an optical probing technology referred to as electro optical probing (EOP) or electro-optical frequency mapping (EOFM) is known. In the optical probing technology, light emitted from a light source is irradiated an integrated circuit, and the light reflected by the integrated circuit is detected by an optical sensor to acquire a detection signal. Then, in the acquired detection signal, a desired frequency is selected, and amplitude energy thereof is displayed as time progression or two-dimensional mapping is displayed. Accordingly, a position of the circuit operated at a desired frequency can be specified.